I suspect a real challenge for local stores is potential customers taking up staff time in getting recommendations and getting to try out stuff and then going home and ordering what the store recommended on line to save a few dollars. I guess those customers think they are getting the best of both worlds - knowledgeable advice from the local store and good prices from the on-line store.
If the store cannot price match, then yes, that is a problem.
The reason they cannot price match is because they have higher overhead costs by providing hands on try outs by consumers.
B&H, Adorama, and Best Buy also have physical locations, high rent overheads, and allow customers to physically fondle merchandise before purchasing.
It's a matter of what volume being supported by online sales. It is dubious how much longer Best Buy can continue the practice. Stores like Fry's long ago stopped the practice but they still cannot survive the onslaught of the internet.
Fry’s has been circling the drain for years now not because of online competition, but because of poor business management and destroying relationships with manufacturers and creditors to the point where they are operating on a pure consignment model now, that has led to rows and rows of empty shelves in the stores that are still open.
Comparatively speaking, Best Buy is doing quite well as a consumer electronics retailer. They have survived other companies like CompUSA, Incredible Universe, Circuit City, Goodguys, and Radio Shack by being more forward looking and leveraging their online sales strategy with their brick and mortar locations, which gives them the best of both worlds in retail.